This application addresses a challenge area (06) Enabling Technologies and a specific challenge topic: 06-HL-103, New Imaging Methodologies to Track Cells. The long term goal of this study is to develop a molecular imaging system, using magnetic resonance imaging (MRI) technique, to track stem cell dynamics after transplantation in the heart. Cell transplantation using derivatives of adult or embryonic stem cells (ESC) is a promising therapeutic approach for heart failure. Stem cell imaging is essential to understanding of biological mechanisms of cell replacement therapy in vivo, and its key challenges are to accurately estimate cell numbers and to track their distribution over time. While MRI is well suited for serial in vivo studies of cardiac structure and function, stem cell labeling with MRI-visible nanoparticles does not provide long term information about survival and expansion. Molecular tagging of graft cells using overexpression of ferritin, a non-toxic iron-binding protein, may solve this problem and enable longitudinal tracking of stem cell distribution and growth after engraftment. The potential of using ferritin overexpression for cardiac stem cell imaging has not yet been explored. Our pilot studies have shown the feasibility of ferritin over expression in a model stem cell system and the successful detection of transduced cells by MRI after transplantation into the infarcted mouse heart. Ferritin overexpression did not affect cell viability, proliferation and differentiation. In this proposal, we will test the hypothesis that ferritin overexpression can be used to non-invasively track therapeutic human ESC derived cardiomyocytes engrafted into the infarcted heart. In Specific Aim 1 we will develop a robust method of ferritin overexpression in human embryonic stem cells for MRI detection in vitro and in vivo. Human ESCs will be lentivirally tagged with ferritin and tested for their ability to form healthy cardiomyocytes, visible by MRI in vitro. We then will evaluate the MRI signal features associated with ferritin labeled human cardiomyocytes after transplantation into the infarcted rat heart in vivo, focusing on the relationship of the MRI signal to viable cell numbers and spatial distribution, and determine how the signal changes as a function of cell division and time. Histological assessment will provide a gold standard correlation. Studies in Specific Aim 2 will use the ferritin tagging system for test strategies to improve survival and growth of human cardiomyocyte grafts after cell transplantation. Specifically, we will test the ability of the hyaluronic acid-based hydrogel, Extracell, to promote the survival and expansion of hESC derived cardiomyocytes in the infarcted rat heart. If successful, ferritin tagging could provide a generally useful approach for high resolution tracking of stem cell dynamics and biodistribution in multiple systems. PUBLIC HEALTH RELEVANCE: Heart failure due to myocardial infarction is a major cause of death worldwide. Stem cell transplantation is a promising therapeutic approach for heart failure. New imaging technologies are essential to enable longitudinal non-invasive studies of grafted cells viability and growth. The long term goal of this study is to develop a molecular imaging system to track stem cell dynamics after transplantation into the heart.